1. Field of the Invention
The invention relates to hand-held apparatus for wipingly applying liquid herbicide to undesired vegetation.
2. Prescription of Prior Art
Several devices have been devised for wipingly applying liquid herbicide to undesired vegetation. Since liquid herbicides tend to be expensive, tend to kill most forms of vegetation they contact and can cause environmental damage if applied excessively, it is highly desirable that applicators dispense only the minimum effective amount of herbicide, at the location desired without significant spillage or wastage. It is further desirable that the wiping element be durable to abrasion, and easily inexpensively replaceable when worn-out. As with any mechanical apparatus, it is further desirable that, consistent with efficient function, such applicator be designed with a minimum number of parts which would increase initial fabrication costs or maintenance of the applicator. Prior art devices have been only partially successful at achieving the above goals. As will be seen prior art designs relied on use of relatively large "wicking elements", which had to become saturated with a relatively large amount of herbicide before the element would efficiently transfer herbicide to vegetation. When use of the applicator was finished, a large amount of herbicide remained in the element, to evaporate and be wasted. Additionally, prior art wicking elements were excessively permeable and tended to leak or apply excess herbicide unless a means for controlling excess herbicide flow was provided. Various means previously used to control flow were air valves, liquid valves or restricting orifices, which increased initial costs, and maintenance, yet were imprecise in regulating flow and had to be constantly monitored.
Laughlin, U.S. Pat. No. 3,002,319 discloses a combination weed cutter/abrader to which a herbicide applicator was attached. The applicator consisted of a chemically impregnated pad which may be fed from the reservoir.
Patrick, U.S. Pat. No. 4,017,986 discloses a hand-held applicator for dabbingly applying liquid herbicide to woody vegetation. The applicator head consisted of several layers of sponge type material covered with a durable rug type covering. On each use of the applicator after being stored, the sponge material and covering had to be saturated with herbicide before it would "wick" effectively. At the end of use the amount of herbicide saturating the sponge and cover would be retained by those elements, and be wasted, by evaporation during storage. Because of excessive permeability of the applicator head, the applicator was provided with a orifice plate and a means for controlling vacuum in the reservoir.
Keeton, U.S. Pat. No. 4,276,718 discloses a hand-held applicator comprising two containers, a metering valve and a roller having a fibrous covering. On initial use the fibrous roller absorbed a large amount of herbicide before it would function effectively. On application of herbicide the roller would become too dry and have to be inserted, and rotated, in one of the containers for rewetting with herbicide. The metering valve somewhat restricted the roller from becoming excessively wet, if used properly.
Maddock, U.S. Pat. No. 4,291,491 discloses a hand-held applicator comprising a reservoir, a handle-conduit and a wicking head. The wicking head comprised a sponge type wick attached to a rigid dispensing tube. On initial use after storage, the wicking element had to be saturated with herbicide before it would work properly, which amount of the herbicide would be wasted, by evaporation, on restorage. Because of excess permeability of the sponge the handle was provided with a metering valve. The sponge type material was not durable to abrasion and its width made the applicator not well suited for application of a very narrow strips of herbicide, such as is desired when edging sidewalks or driveways.
Maddock, U.S. Pat. No. 4,357,779, discloses a hand-held herbicide applicator somewhat improved by addition of an outer skin to retard outer wetting the wiping head sufficiently to promote even saturation of the sponges interior. The sponge still requires a substantial, wasted quantity of herbicide to accomplish saturation of the sponge. Flow control is still provided in an attempt to solve the problem of excess permeability of the saturated sponge.
Maddock, U.S. Pat. No. 4,305,224 discloses a hand-held herbicide applicator comprising a reservoir, tubular handle-conduit, metering means and one or more elongated wicking elements. The wicking element absorbed herbicide until, by wicking action, became saturated, then a user could apply herbicide to vegetation. Because of excess permeability of the wicking element flow control means, consisting of an air valve and a liquid valve, were provided.
Keeton, U.S. Pat. No. 4,403,881 discloses a hand-held herbicide applicator comprising a handle-reservoir and a sponge-type applicator held in a slitted, rigid tube. The applicator head is not bendably conformable to different shapes and use of sponge-type material resulted in use of significant quantities of herbicide for wetting of the sponge. Flow control means is provided in attempt to solve the problem of excess permeability of the applicator head.
Kroph, U.S. Pat. No. 4,597,219 discloses a hand-held herbicide applicator comprising a handle-reservoir and a head composed two wicking means, the outer wicking material being non-woven fibrous chamois material. The head is not bendable conformable to various shapes. To control excess flow a small hole or orifice is provided between the reservoir and the first wicking means.
Struve, U.S. Pat. No. 4,727,678 discloses a hand-held applicator comprising a tubular handle-reservoir and fibrous paint roller which is partially exposed through a window in an impermeable shield. The paint roller, on initial use after storage, must become saturated with herbicide to function properly, which said saturation quantity is wasted on re-storage. When the roller became over-saturated the user is supposed to be invert the applicator to allow some herbicide to drain back into the handle.
Also appearing in prior art are devices which were not designed or used for wipingly applying herbicide to vegetation, but rather were designed for underground irrigation.
Mason, U.S. Pat. No. 4,517,316 discloses uniformly porous irrigation piping designed for underground burial. The piping is made of screened crumb rubber, of uniform water content, combined with a termoplastic binder resin. By controlling the temperature and rate of extrusion, the water vaporizes during extrusion and the expanding bubbles of steam in the binder resin form a network of pores which allows the pipe to leak, or weep, uniformly.
Mason, U.S. Pat. No. 4,616,055 discloses similar porous irrigation piping with improved pore consistency and strength.